squirrelmail and exim send problem

["Benedict Verheyen" <benedict.verheyen@pandora.be>]

Hi,

i've set up fetchmail, exim4, courier-imap and squirrelmail. I can 
read my mail via the web by using a domain name that i registered
with ddts.net that points to my server at home. 
But i cannot send mail from my webinterface. I tried to use the SMTP 
method and the sendmail method. I can get the sendmail method working 
by adding an alias for user www-data to the /etc/email-addresses file 
but that makes the sendmail useless as other users cannot send mail 
since the sent mail will all appear to be from me (i've added my real 
email address after the www-data user).

I see this in the email headers: Sender: www-data <www-data@camelot>
and (SquirrelMail authenticated user benedict)
So is there a method to let squirrelmail figure out that the 
sender is actually benedict@camelot and not www-data@camelot?

When i try the smtp method i get this as error message:

2003-10-09 14:27:33 rejected EHLO from arthur.camelot [192.168.0.1]: 
syntactically invalid argument(s): <domainname>.ddts.net:<apacheport>

So neither method works how can i fix this?
Any ideas?

Thanks
Benedict